So-called fill-and-pack in a non-germ atmosphere methods are frequently desirable in comparison to regular methods. The fill-and-pack in the non-germ atmosphere method may involve sterilizing food prior to filling the food into a container and then sealing the container with a lid in a non-germ atmosphere. The container and the lid are also sterilized beforehand. Regular methods, on the other hand, involve filling and packing in a clean atmosphere, which contains germs, and sterilizing the food and the container together by applying heat or hot water thereafter.
The former method is considered better than the latter one for the following reasons:
.circle.1 Food is sterilized with high temperature in a very short time, therefore the quality of the food remains good for a long time.
.circle.2 Since food is sterilized and filled in a sterilized container, it contains no germs, and therefore will not rot even if it is kept long time at normal temperatures.
.circle.3 Keeping food cold is not necessary, so that energy otherwise needed for cooling the food can be saved.
.circle.4 Food can be filled in a bigger container than a can for canned food. Thus it is more economical.
.circle.5 Food can be saved in a warehouse and on a shelf for a long time, thus production of the food can be well planned.
.circle.6 The container is sterilized by means other than heat before the food is filled, therefore heat-proofing is not required.
There are at least two ways to complete the method for fill-and-pack in the non-germ atmosphere: one is to seal the container with a film-like lid material and cut it to a lid shape thereafter; the other is to seal the container with a lid that has previously been cut or punched to a lid shape.
The former type, however, has a number of problems. For example, it is extremely difficult to keep the non-germ atmosphere of the apparatus since it is necessary to create an open passage between the inside and the outside of the apparatus to supply the film-like lid material. Therefore, the latter type is considered more convenient.
The latter type--previously cut a lid in shape--is described in Japanese patent application No. 54-115221. In this invention, each lid is held by a rod which moves by an endless chain, and as the lid moves it is sterilized, dried and then supplied on the container for sealing. After the lid is put on the container, it moves to a next step and there the lid is pressed by hot heat and sealing is completed.
The problem of this invention, however, is that since the container moves with a lid to the next hot press step, the lid often moves from the first set position and the lid then can be sealed on the wrong distorted position. This could produce incompletely sealed products having poor appearance.
Japanese patent No. 57-193602 attempts to resolve the above-mentioned problems by including means that correct the position of the lid put on the container, and other means that temporarily seal the lid onto the container by pressing hot heat on some spots of the lid.
However, this invention also has a number of problems to be solved. They are as follows.
.circle.1 In the lid sterilizing process, the lid holder's capacity is limited to holding only one shape of lid. Thus when a different shape of lid is supplied, all of the lid holders have to be replaced by another type. Moreover, when replacing the lid holders, the non-germ atmosphere may be disrupted. Both replacing the lid holders and recreating the non-germ atmosphere take time and money.
.circle.2 Since a part of the endless chain takes place outside of the apparatus, maintaining a non-germ atmosphere is extremely difficult. Preventing hydrogen peroxide gas, which is used for sterilization, from entering into the non-germ atmosphere is also difficult.
To prevent the disruption of the non-germ atmosphere, it is necessary to keep the pressure of the passage that connects the outside, the sterilizing room and the non-germ atmosphere room, higher than outside to prevent the outside air from flowing to the inside. Also it is necessary to prevent the hydrogen peroxide gas from entering into the non-germ atmosphere room or leaking to the outside. At the same time, keeping the hydrogen peroxide gas in the sterilizing room for a certain period of time is essential to adequately sterilize the lid. Unfortunately, all of these requirements cannot well be accomplished by the prior art.
.circle.3 Since the hydrogen peroxide gas cannot be kept in the room for longer than a certain period of time, density of the gas is required to be up to about 50 percent for instance. As a result, the gas could remain on the lid and the food could be deteriorated.
.circle.4 Since the lid holder does not possess the ability to move, means that can move the lid from one place to another is included. As a result, the structure of the apparatus is more complicated and moreover correct positioning of the lid on the container is difficult to achieve.
It is possible to include means that correct the lid's position, but this makes the structure of the apparatus complicated and costly.
.circle.5 While the lid is held by the holder, the sterilizing and the drying processes are carried out. Therefore, at least part of the lid is held and thus hidden by the holder, so that it cannot adequately be sterilized or dried.
.circle.6 The means for correcting the lid's position and for sealing the lid temporarily are mechanically connected. Thus, when a differently shaped of lid is supplied, the means has to be adjusted by hand. While adjusting, therefore, the non-germ atmosphere will be disrupted. It takes time and work to recreate the non-germ atmosphere.